Heavy metal contamination of surface sediments along the Moroccan Coast from Tangier to Saïdia

This study aims to assess heavy metal contamination levels in surface sediments along the Moroccan Mediterranean coast, analyzing its temporal evolution and associated ecological risks. Accordingly, concentrations of eight heavy metals (Cd, Cu, Cr, Ni, Pb, Zn, Fe, and Mn) were measured at nine distinct sites over three distinct time periods (2015, 2016 and 2017). The results obtained showed notable geographical and temporal variations in heavy metals concentrations. The use of environmental and ecological indices (PLI, mCd, Igeo, EF, and RI) indicated that there is an increasing trend of Pb and Zn content in sediment collected from Oued Selouane and Kariat Arkmane. In contrast, Oued Fnideq indicated a decline in all heavy metals content except for Pb, which showed a slight increase in 2017. All sampling sites during the three periods showed risk index values below 150, suggesting a low potential ecological risk associated with the studied metals. Except for Pb and Zn, all metals showed Nil and rare adverse effects on marine organisms. Adverse effects occasionally occurred due to Pb, as reported for Oued Selouane and Kariat Arkmane sediments, while toxic effects are frequently observed associated with Zn concentrations found in Oued Souani, Kariat Arkmane, and Oued Moulouya. This suggests further investigations of Zn and Pb occurrence in the investigated zones sediments. These results provide information about the quality of the Moroccan Mediterranean coastal ecosystem.